Mineralizaciones asociadas a rocas ultrabásicas en el Hercínico español

Se han estudiado las mineralizaciones asociadas a las rocas ultrabasicas del complejo de cabo ortegal (macizos de limo, herbeira y uzal y serpentinitas de moeche-ortigueira); las rocas ultrabasicas del complejo de ordenes y las mineralizaciones asociadas a las serpentinitas de calzadilla de los barros en ossa morena. En los macizos de limo, herbeira y uzal (complejo de cabo ortegal) las mineralizaciones se restringen al tercio occidental del macizo de herbeira, constituido por litologias dunitico-piroxeniticas dominantes. La mineralización esta formada por bandas y schlieren cromiticos intercalados entre estas litologias. En clara relacion con estas bandas de cromita se han hallado mineralizaciones de e.g.p. (platino + paladio). En las serpentinitas de moeche-ortigueira (complejo de cabo ortegal) se han hallado mineralizaciones de cromita podiformes, en relación con macizos punitico-harzburgiticos totalmente serpentinizados. Las mineralizaciones son tanto de alto contenido en cromo como de alto contenido en aluminio. Las mineralizaciones de las serpentinitas de calzadilla de los barros son de tipo podiforme, en relación con macizos punitico-harzburgiticos. Se trata de cromititas de tipo refractario, (alto contenido en aluminio). Las rocas ultramaficas del complejo de ordenes muestran escaso potencial en cuanto a mineralizaciones de crom

Relevance of the mineralogical characterisation of serpentinites for their use as dimension stone: an example from Galicia, Spain

[EN]Workers carrying out actions involving potential hazards, like mining and quarrying, can be subject to health issues derived from those activities. The case of asbestosis has generated an alarm in the society. Natural stones are very different from each other and generalisation can cause, first an unwanted alarm, and secondly a big economic crisis in the sector of the natural stone, as it has happened before with other health issues related to exploitation and use of natural stone in architecture. This paper highlights the need for an appropriate mineralogical characterization of rocks of economic interest, such as serpentinites, to protect mining workers of health issues derived from fibrous minerals content. We have studied the possible presence of fibrous minerals in samples of serpentinites from an abandoned quarry in Galicia (North Western Spain) to consider the viability of its re-opening based on the Spanish health and safety regulations applicable to jobs at risk of exposure to asbestos. From our study, it can be concluded that there is a scarce amount of fibrous phases, pending on further studies to differentiate such fibrous minerals, and therefore the reopening of the serpentinite quarry should not be a health problem for the workers

The Importance of Preserving Small Heritage Sites: the Case of La Tuiza Sanctuary (Zamora, Spain).

[EN]For centuries, granite has been one of the most widely used natural stones for building heritage, especially in the north of the Iberian Peninsula. The sanctuary of La Tuiza in Lubian (Zamora, northwest of Spain), built with Calabor granite, dates from the eighteenth century and was declared an Asset of Cultural Interest in 1995. The heritage importance of this site lies in its location, on the Sanabria route (Silver Route) of the Way of St James (Camino de Santiago), attracting visitors from all over the world. This work presents the complete characterisation of the building stone of both the monument and the original quarry and the qualitative description of the main pathologies that have been detected. The capillary water absorption coefficient is twice the value in the sanctuary compared to the quarry; the open porosity, water absorption at atmospheric pressure and sound speed propagation are slightly higher, and the compressive strength value is lower in the stones of the building. These differences reveal the incipient decay processes. In terms of pathologies, biological colonisation is scattered throughout the building, affecting the north face more intensely, and on the exterior, scaling is observed on the west face. Inside the sanctuary, deterioration is related to humidity due to capillary water infiltration, which causes conspicuous stains, efflorescence and biological colonisation in the western sidewalls. The authors recommend that measures be taken to prevent further deterioration and to protect this small site in order to maintain the cultural heritage linked to the local community.GIR CHARROCK The research was conducted in the frame of the European Region Development Funding (FEDER) to the Territorial Service of Culture and Tourism of Zamora, Junta de Castilla y Leon (Regional Government)

Caracterización químico-mineralógica de las cromitas ofiolíticas de Calzadilla de los Barros (Badajoz)

The Cerro Cabrera and Sierra Cabeza Gorda peridotite massifs (Calzadilla de los Barros, Badajoz) comprise serpentinites hosting podiform chromite mineralization and have been interpreted as part of an ophiolitic slab. The chromites are Al-rich and cristallized from a MORB-type melt. The subsolidus reequilibration with olivine depleted the chromite margins in Al and Mg. Later metamorphic alteration produced a enrichment in Fe3+, resulting in the formation of ferrichromite

Geotecnia en píldoras: información en dosis para un aprendizaje autónomo de la geotecnia de laboratorio

Memoria ID-111. Ayudas de la Universidad de Salamanca para la innovación docente, curso 2019-2020

Interferencia entre la investigación y las actividades docentes: ¿problema u oportunidad?

Memoria ID-161. Ayudas de la Universidad de Salamanca para la innovación docente, curso 2018-2019

Caracterización petrológica y geoquímica de las rocas ultramáficas del macizo de Herbeira, complejo de Cabo Ortegal (NO de España)

The uppermost unit in Cabo Ortegal complex is composed of ultramafic rocks that crop out in three massifs: Herbeira, Limo and Uzal. Herbeira massif shows two different areas separated by a NNE-SSW fault zone. The western area is formed by a layered complex of dunites and pyroxenites which lies on top of a basal harzburgite. Amphibole-bearing peridotites and hornblendites; with aluminous spinels (Cr#<0.4), are the main lithologies in the eastern area. Hornblende is invariably present in all types of ultramafic rocks in the Herbeira massif, but the eastern peridotites mostly contain more than 15% of amphibole. Almost all ultramafic units show light rare earth elements (LREE) enriched patterns, however the basal harzburgite shows LREE-depleted patterns with negative slope while the rocks from layered complex are LREE enriched. Both ultramafic rocks from Herbeiia present marked significant Nb and Zr negative anomalies. The mineral chemistry, the REE abundances, geological and petrological data for Herbeira suggest a open-system melting to explain the formation of ultramafic rocks. The appropriate geodynamic scenario is a mantle wedge above a supra-subduction zone where the influx of an exotic fluid/melt generated in the upper parts of the subducting slab produces melting and melt extraction in the overlying mantle wedge

Structure and Mechanical Properties of the Dueñas Clay Formation (Tertiary Duero Basin, Spain): An Overconsolidated Clay of Lacustrine Origin

The Dueñas Clay Formation is considered an example of a deposit of lacustrine continental origin. It is formed mainly by overconsolidated clays and includes feldspathic arenites, and clayey and silty levels; however, in geotechnical projects it is considered a clay unit and treated as a whole. The structure of each level was assessed in the field, in thin sections, and by SEM in the case of the clayey level. In addition, identification, strength, deformation, and durability tests were undertaken according to the nature of the samples (grain size analysis, Atterberg Limits, point load test, direct shear tests, uniaxial compression tests, swelling pressure, and unidimensional consolidation tests). The durability test was used as a criterion for dividing the levels within the formation according to their behavior as soil or rock. It was observed that the proportion and type of carbonate cementation controls the way in which the material behaves, with sparithic cement increasing the strength. The clay levels are expansive due to the presence of smectite, which also influences their behavior under shear stress. In addition, the massive and laminar structure of the layers caused by the continental conditions, in addition to the processes of post-sedimentation, explain their low compressibility

Creación de modelos a escala de situaciones reales en distintas obras para estudiar el comportamiento geomecánico de materiales granulares y cohesivos

Memoria ID12-0264. Ayudas de la Universidad de Salamanca para la innovación docente, curso 2012-2013